Old 04-12-2011, 10:57 AM
  #8  
SunnyFlyer09
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Default RE: Thrust Figures For Norvel .049 and .061


ORIGINAL: MikeSell

I have several of these engines and use them to fly different types of planes. The thrust they produce is totally dependent upon the prop installed. Prop diameter and pitch as well as efficency effect thrust greatly.

With the right pitch and diameter these engines will indeed turn 25,000 RPM but thrust will be down because their torque peak is at about 17-18,000. That prop is not exerting the resistance necessary to load the engine. It will make the engine spin fast and possibly make a small plane fly fast but will not produce the most thrust. A prop that will not allow the engine attain close to 17,000 rpm is lugging the engine an is not producing maximum thrust. Trimming the diameter of the blade just enough to allow the engine to hit its torque peak should increase thrust.

The airfoil and rigidity of the prop blades are the other major factors. A thin airfoil has less wind resistance than a thick one but usually a thick airfoil has more lift. The efficency (resistance vs lift) controls if the increase iin RPM will yield more lift which translates to thrust.

The correct diameter/pitch/efficency combination may or may not produce the most thrust depending if the blade flexes out of spec under load. Flexable props are wonderful on planes with no landing gear or in crashes. In demanding applications more rigid ones are always preferred.

It would take some prop testing to find what is the maximum thrust of these engines with the available props. Your question as stated is much like ''With 120v power supply how hot will my hot plate get?''

I get enough thrust from my .061 norvel to fly a 52'' span high drag airframe at a 45 degree climb indefinately. With the same engine but a different prop of different manufacture, but the same diameter and pitch, the plane hasn't enough thrust to maintain level flight.
So what is all the hype about getting these engines up to 30K for pylon racing? If you are 12k past the torque curve, what is the benefit ?